In a brutally frank 17-minute testimonial uploaded to YouTube, Seavey, 30, repeatedly denied that he gave his dogs the drug and said someone could have spiked his dogs' food supply during the grueling 1,000-mile race.
"I believe this [drug] was given to my dogs maliciously," he said.
Seavey's surname is well known in the musher racing world: He is the son of three-time champion Mitch Seavey, 58.
In the video, Dallas Seavey, an Alaska native, repeatedly condemned the Iditarod Trail Committee's board of directors for publicly assassinating his character, saying, "I have spent the last 10 years becoming the best musher I possibly can. I've done nothing wrong."
Two weeks after Iditarod officials announced that several racing dogs tested positive for a banned drug, speculation swirled over who was "Musher X."
It's the first time the famed Alaska sledding race went public with dogs' testing positive for doping.
News that Seavey was "Musher X" came after an emergency meeting in which 83 current and former competitors belonging to the Iditarod Official Finishers Club signed a statement calling on the board to name the tainted musher within 72 hours.
In his video, Seavey, a top-ranked dog racer, said his team "had a drug test" and attempted to work with race officials to "get the information out there."
He said he was duped and he was caught off guard by the committee's public declaration of the alleged dog doping, saying he thought race officials would address the issue by instituting fixes and tighter security.
"I believe that they had come to that conclusion that I had been cleared of all wrongdoing," he said. "They were going to protect our food drops. They were going to have surveillance [added] at checkpoints."
It's unclear if any of these measures have been instituted.
"The Iditarod can try to run me over," he said. "They can try to throw me under the bus. But I'm going to be honest with myself, and they are going to find out I don't fit under the bus."
Seavey said that he has "never knowingly broken any race rules" and that he has "never given any banned substances to my dogs."
The rules, which were updated this month, bar racers from using any kind of injectable, oral or topical drugs to mask injury or "to drive a dog or cause a dog to perform or attempt to perform beyond its natural ability."
Mushers must submit their dogs' urine or blood samples for testing up to six hours after the team's finish.
Competitors are required to protect their dogs' food from being tainted, and they are "strictly liable for all positive tests for prohibited drugs and procedures of dogs in their team," the rules state.
Accused mushers could be forced to take a polygraph test, and if anybody is found to sabotage other mushers or their dogs, directly or indirectly, he or she "will be subject to discipline of disqualification and/or a ban," the rules read.
Seavey said he is determined to sideline himself for good if that's what it takes to get at the truth.
"I don't care if I never race another dog race," he said in the video. "I don't care if I make another cent, which is my life, this sport."
He continued, "I will not spend the rest of my life looking in the mirror knowing that I backed down when I did nothing wrong."
Seavey acknowledged that his releasing the video response was a direct violation of the governing board's prohibition on discussing internal race matters.
"I fully expect that after this I will be banned from the Iditarod, based on the gag rule," he said, as he threw his hands up. "I have no choice, though."
So far, Seavey hasn't been sanctioned because the board couldn't prove intent, according to a statement it released.
He took second place in this year's race, behind his father.
Chas St. George, an Iditarod spokesman, told The Associated Press that race officials "can't rule anything out."
Before naming Seavey, Iditarod officials said in a statement Monday that a drug testing team collected urine samples from four of the unnamed musher's dogs in Nome, Alaska, six hours after the team completed the race.
The sealed urine samples were shuttled to a lab two days later, where they twice tested positive for tramadol, the statement said.
Iditarod board member Aaron Burmeister told the AP, "It's not a good situation. I'm hoping that we can turn a positive light on it and the musher steps forward."
When Seavey learned he was under investigation for allegedly doping his dogs, he said, he was on an overnight camping trip with his daughter Annie.
"I get the worst phone call of my life," he said in the YouTube video.
He went on to say, "I personally have never administered" tramadol.
Seavey said he did an audit with his team and kennel and found that he was clean.
"I know I'm supposed to say I accidentally gave this to my dogs, but I have to tell you there is less than a half-percent chance that that happened," he said in the video.
Seavey said he was willing to be questioned with a polygraph and risk his livelihood for other racers.
"I tried to cooperate fully," he noted. "I apologize to my fellow mushers that this race is about to hit a rough patch. I love the Iditarod ... The board is not the Iditarod."
ABC News has reached out to Dallas Seavey and Mitch Seavey for comment. Officials from the Iditarod Trail Committee did not immediately respond to ABC News' request for comment.